1. Field of the Invention
The present invention relates generally to a liquid crystal display device, and more particularly to a liquid crystal display device which is configured to be capable of realizing both a wide viewing angle and a narrow viewing angle.
2. Description of the Related Art
In recent years, mobile phones, which can display mail and images, have widely been used. In using such mobile phones, there have been increasing needs for preventing a displayed image from being peeped at by persons around the user.
To satisfy such needs, Jpn. Pat. Appln. KOKAI Publication No. 2004-062094 (Patent Document 1), for instance, proposes a structure wherein a liquid crystal plate for varying a viewing angle is superposed on the front surface of a liquid crystal display (LCD). According to the structure of Patent Document 1, however, it is difficult to restrict omnidirectional viewing angles, because of the effect of viewing angle characteristics of the liquid crystal plate for varying the viewing angle. Moreover, the addition of the liquid crystal plate for varying the viewing angle leads to demerits such as an increase in cost, thickness, weight and power consumption.
Jpn. Pat. Appln. KOKAI Publication No. 2003-295160 (Patent Document 2) and Jpn. Pat. Appln. KOKAI Publication No. 2004-318112 (Patent Document 3) propose structures wherein a lookup table is provided for adjusting a distortion of a gradation curve on a display screen due to viewing angles, and display data is generated on the basis of a result of the reference to the lookup table. According to Patent Document 2 and Patent Document 3, a screen image is displayed with a wide viewing angle range (a wide viewing angle) by making such adjustment as to decrease a distortion of the gradation curve due to viewing angles, and a screen image is displayed with a narrow viewing angle range (a narrow viewing angle) by making such adjustment as to increase a distortion of the gradation curve due to viewing angles.